THE state government has called for community feedback on a plan to extend the South West Rail Link to Badgerys Creek and Narellan.

The government plans to reserve a corridor, with room for six new train stations: Badgerys Creek, North Bringelly, Bringelly, Rossmore, Oran Park and Narellan now, even though the federal government has said the train line will not be completed when the second Sydney airport opens at Badgerys Creek in the 2020s.

Minister for Infrastructure and Regional Development Warren Truss said the airport would be designed to accommodate a train line in the future, but it would not be required when the airport first opens.

The new corridor will continue the South West Rail Link from the new Luddenham station, which will start operating in 2015, through to the Western Line station of St Marys and south to Narellan.

NSW Transport Minister Gladys Berejiklian said the future rail corridor will link jobs, service hubs and communities in the south-west with Sydney's existing and future public transport and roads networks.

"To begin with — when the airport's air traffic will be less than 10 per cent of that of Sydney airport — access to the second Sydney airport will be provided through road upgrades, park and ride facilities and public transport services including new express buses," she said.

Initial projections showed an airport at Badgerys Creek would carry about 3 million passengers each year, similar to the capacity of Canberra and Hobart airports.

Ms Berejiklian said the public transport demands of much larger airports, like Melbourne International Airport, are met by a fleet of express buses.